Because of their operating principle of discontinuous combustion of fuel in the combustion spaces of cylinders or combustion chambers provided for that purpose, combustion engines have a non-uniform torque development through the angle of rotation of the crankshaft. The torsional vibrations, which occur as a result, are isolated in a well-known manner by torsional vibration dampers such as clutch plate dampers, divided flywheels and the like, and/or torsional vibration absorbers such as centrifugal force pendulums and the like. This vibration isolation occurs only partially. Remaining residual vibrations appear in resonance with natural frequencies of the power train, which result in negative sound behavior of the drivetrain and/or negatively affect the service life of the components used. To further improve the degree of isolation, the technical effort increases, so that the isolation devices to be utilized, such as torsional vibration dampers or torsional vibration absorbers, cannot always be implemented for reasons of construction space and/or cost. For example, in a torsional vibration damper, besides the utilized bow springs of a single damping stage, additional damping stages, an additional torsional vibration absorber matched to the torsional vibration damper and the like may become necessary. Furthermore, the driver may introduce impulses into the drivetrain, for example, with the respective changing of the position of the accelerator pedal, which can result in jerking or load reversal vibrations.
In addition to the combustion engine, hybrid drivetrains have an electric machine which drives the drivetrain completely or partially, recuperates in deceleration mode, and is able to start the combustion engine. An electric machine is known from German Patent No. 195 32 129 A1, which is intended to compensate for torsional vibrations of the combustion engine by switching on opposing torques by means of the electric machine, which are complementary to the peak torques of the combustion engine. The corresponding quantities of energy in the frequency range of the torsional vibrations to be stored temporarily in and recalled from the accumulator connected to the electric machine, such as a lead-acid battery, result in very high charging and discharging currents, which are harmful to the accumulator.